The major thrust of this study continues to be the epidemiology and clinical expression of Chlamydia trachomatis infection in our population with a focus on perinatal infections. We intend to evaluate the efficacy of erythromycin in preventing the transmission of C. trachomatis from the infected pregnant woman to her newborn infant. Through serologic surveys and chlamydial isolation attempts we will try to determine if there is any clinical expression of the seroconversions that have been demonstrated for C. trachomatis in older children (ages 5 through 10) and attempt to evaluate the contribution C. trachomatis may make to respiratory disease, particularly pneumonia in adults.